1. A circle C, with origin as centre, touches line 3X+4Y=25.
a) Find equation of C.
b) Show that C also touches line 4x-3y=25.
c) Find equation of tangent to C at P(3,-4).
ce a.maths CO-GEOM(CIRCLE) 2
2007-12-04 4:51 am
回答 (1)
2007-12-04 5:05 am
✔ 最佳答案
a.distance between origin and the line:絕對值(-25/開方3^2+4^2)
=5
THe requried eqn.:x^2+y^2=5^2
b. distance between origin and the line=絕對值(-25/開方3^2+4^2)
因為distance=radius
所以touch
c.slope=(-4-0)/(3-0)
=-4/3
所以tangent slop=3/4
y-(-4)=3/4(x-3)
3x-4y-13=0
2007-12-03 21:06:16 補充：
d tnhe ?
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